1. Field of the Invention
The present invention broadly relates to computer systems, and more particularly, to a computer system where one circuit board is vertically mounted on another circuit board using a torque-limiting screw.
2. Description of the Related Art
A computer system generally comprises a number of circuit boards, which carry a large number of electronic components mounted thereon. A motherboard in a computer system is one such typical circuit board. The motherboard carries one or more processors (or "microprocessors") along with a number of memory modules inserted into corresponding sockets provided on the motherboard. A motherboard may further include a number of high density sockets, i.e., sockets having a large number of conducting paths. An external circuit board may be inserted into a high density socket on the motherboard to extend, e.g., memory capacity, of the computer system. The external circuit board may be inserted into the corresponding socket on the motherboard manually with or without further tightening by a screw.
Current screw designs, however, allow a user to "overtighten" a screw such that the user may continue rotating the screw head and advancing the screw even when the two objects to be fastened with the screw are already properly fastened. This overtightening may sometimes result in breakage or damage of one or both of the objects being fastened by the screw. This may not be desirable in certain applications, e.g., where two circuit boards in a computer system are to be fastened, or where the breakage or damage may be expensive or time-consuming to repair. Further, the overtightening may result in blunting of the grooves within the screw receiving surface, which may result in a permanently loose joint unless some additional measures are taken to maintain the screw rigidly fastened. Additionally, a loose screw may fall off the joint during transportation or due to vibrations.
In some applications, a circuit board that is vertically mounted on the motherboard may have a high density connecting edge that requires a high engagement force and a small engagement distance during insertion into a corresponding high density connector socket on the motherboard. It may therefore be desirable to limit the applied torque to prevent overtightening while inserting one circuit board into a socket on another circuit board, e.g., the motherboard, using screw type threaded fasteners.